Link adaptation and antenna selection in cooperative multiple access systems

ABSTRACT

Embodiments of the present invention provide techniques for applying link adaptation and antenna selection in cooperative multiple access systems where multiple user devices act cooperatively to communicate with a network access station through a MIMO channel.

TECHNICAL FIELD

Embodiments of the present invention relate to the field of wirelesscommunications, and, more specifically, to techniques for improvingmultiple access in a wireless system.

BACKGROUND

Wireless communication systems are experiencing an explosive growth inpopularity. This increase in popularity has fueled a demand for wirelessnetworks capable of providing high capacity, high quality, and powerefficient voice and data communication. One such technology is multipleinput, multiple output or MIMO. In a MIMO system, multiple antennas areutilized at each end of the point-to-point wireless link. This multipleantenna infrastructure allows known practical techniques to be utilizedfor improving spectral efficiency, link reliability, and powerefficiency. This infrastructure, however, is also a major limitingfactor in MIMO's widespread acceptance and deployment. While MIMOsystems are able to provide higher throughput and reliability than othersystems, their need for multiple antennas, and consequently, complex andcostly RF chains, minimizes their suitability for certain applications.

In a recent patent application, cooperative communication techniqueswere disclosed which allow the advantages of MIMO to be achieved withinsystems using single antenna devices. The term cooperative communicationrefers to scenarios in which distributed radios interact jointly totransmit information in wireless environments. In effect, multiplesingle antenna devices cooperate with one another to appear as a singlemultiple antenna device. This allows the extraction of MIMO benefits ina distributed fashion. Cooperative communications or cooperativemultiple access systems, however, do not allow the application of theknown practical techniques currently used in MIMO systems to achievespectral efficiency, link reliability, and power efficiency. Therefore,similar techniques to those used in MIMO systems, namely antennaselection and link adaptation, are needed for cooperative communicationor cooperative multiple access systems.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings. Embodiments of the invention are illustrated by way of exampleand not by way of limitation in the figures of the accompanyingdrawings.

FIG. 1 is a block diagram illustrating a multi-user wireless networkarrangement;

FIG. 2 is a block diagram illustrating an example cooperative multipleaccess arrangement in accordance with various embodiments of the presentinvention;

FIG. 3 is a block diagram illustrating an example cooperative multipleaccess wireless network arrangement capable of performing antennaselection in accordance with various embodiments of the presentinvention;

FIG. 4 is a block diagram illustrating an example cooperative multipleaccess wireless apparatus capable of performing link adaptation inaccordance with various embodiments of the present invention;

FIG. 5 is a flow chart illustrating an example method of performing linkadaptation and antenna selection in a cooperative multiple accesswireless network in accordance with various embodiments of the presentinvention; and

FIG. 6 is a flow chart illustrating a method of performing linkadaptation within a wireless device functioning in a cooperativemultiple access wireless network in accordance with various embodimentsof the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration embodiments in which the invention may be practiced.It is to be understood that other embodiments may be utilized andstructural or logical changes may be made without departing from thescope of the present invention. Therefore, the following detaileddescription is not to be taken in a limiting sense, and the scope ofembodiments in accordance with the present invention is defined by theappended claims and their equivalents.

Various operations may be described as multiple discrete operations inturn, in a manner that may be helpful in understanding embodiments ofthe present invention; however, the order of description should not beconstrued to imply that these operations are order dependent.

The description may use perspective-based descriptions such as up/down,back/front, and top/bottom. Such descriptions are merely used tofacilitate the discussion and are not intended to restrict theapplication of embodiments of the present invention.

The terms “coupled” and “connected,” along with their derivatives, maybe used. It should be understood that these terms are not intended assynonyms for each other. Rather, in particular embodiments, “connected”may be used to indicate that two or more elements are in direct physicalor electrical contact with each other. “Coupled” may mean that two ormore elements are in direct physical or electrical contact. However,“coupled” may also mean that two or more elements are not in directcontact with each other, but yet still cooperate or interact with eachother.

The description may use the phrases “in an embodiment,” or “inembodiments,” which may each refer to one or more of the same ordifferent embodiments. Furthermore, the terms “comprising,” “including,”“having,” and the like, as used with respect to embodiments of thepresent invention, are synonymous.

Embodiments of the present invention relate to techniques andapparatuses for implementing antenna selection and link adaptivespace-time modulation algorithms in cooperative multi-access networks.In this manner, spectral efficiency, link reliability, and powerefficiency may be obtained for systems wherein devices cooperate withone another in order to appear as a single multiple antenna device. Theinventive techniques may be implemented by both single antenna andmultiple antenna devices. In addition, the inventive techniques may beused within wireless local area networks (WLANs), wireless wide areanetworks (WWANs), wireless municipal area networks (WMANs), localmultipoint distribution service (MMDS) systems, wireless cellulartelephone networks, terrestrial wireless communication networks,satellite communication networks, and/or other types of wireless systemsand networks.

FIG. 1 is a block diagram illustrating a multi-user wireless networkarrangement 10. As shown, first and second wireless user devices 12, 14are each communicating with a network access station 16 in a multipleaccess relationship. The network access station may be either an accesspoint, base station, or other device capable of relaying information toand from wireless devices and wired devices. The network access station16 has finite communication resources available to it for use inservicing users and must allocate these resources amongst the currentusers. Resources may be allocated in a variety of different ways in amultiple access system. Some techniques for allocating resources includetime division multiple access (TDMA) where one or more time slots areallocated to each active user, frequency division multiple access (FDMA)where one or more frequency channels are allocated to each user, codedivision multiple access (CDMA) where one or more spread spectrum codesmay be allocated to each user, orthogonal frequency division multipleaccess (OFDMA) where a subgroup of subcarriers may be allocated to eachuser, spatial division multiple access (SDMA) where a common resourcemay be allocated to two different users concurrently as long asspatially separated antenna beams are used for the two users, andcarrier sense multiple access with collision avoidance (CSMA-CA) whereusers first check to see if a medium is currently busy, transmit if itis not busy, and re-transmit if a collision occurs. Combinations of theabove techniques may also be used. All of these techniques require thedifferent users to “compete” for available resources.

In contrast, embodiments of the present invention relate to techniquesapplicable to cooperative multiple access systems. Cooperative multipleaccess allows multiple users to form transmit clusters that communicateas a single entity with a remote destination device or network accessstation (e.g., a base station, an access point, etc.). By cooperatingwith one another, the devices in the cluster are no longer incompetition with each other for communication resources. Instead, thecooperating devices are assigned a single resource allocation that theymay use cooperatively as if they were a single device. Even if thecooperating devices are single antenna devices, the cooperativearrangement, in addition to the techniques described below, allows thedevices to achieve many of the benefits of MIMO based wireless operation(e.g., spatial multiplexing gain, diversity gain, array gain, etc.). Thecooperating devices within a cluster may include all single antennadevices, all multi-antenna devices, or a combination of single andmulti-antenna devices.

FIG. 2 is a block diagram illustrating an example cooperative multipleaccess arrangement 20 in accordance with an embodiment of the presentinvention. As shown, first and second wireless user devices 22, 24 haveaffiliated with one another as a transmit cluster 28 to communicate witha network access station 16. The cooperating devices 22, 24 maycommunicate with one another via intra-cluster wireless links 26. Thecluster 28 may then transmit data to the network access station 16 as asingle MIMO type unit, via a MIMO channel. The cluster 28 may utilize acommon time/frequency resource allocated by the network access station16 (resource allocation techniques such as, for example, OFDMA,OFDM-TDMA, and/or others may be used). After reception, the networkaccess station 16 may demodulate and decode the data from the cluster 28and separate out the data associated with each of the cooperatingdevices 22, 24.

In at least one embodiment, the receiver within the network accessstation 16 uses a MIMO receiver design. The network access station 16may be able to support other non-cooperating wireless devices and/orother clusters at the same time that it is supporting the cooperativecluster 28. Further, any type of wireless device may be formed into acluster including, for example, computers having wireless capability,personal digital assistants (PDAs) having wireless capability, cellulartelephones and other handheld wireless communicators, and/or others. Inaddition, in at least one embodiment, a single cooperative cluster mayinclude different types of wireless user devices. For example, a clustermay include a cellular telephone and a PDA that cooperate to transmitdata to a network access station. Each wireless user device 22, 24 inthe cluster 28 includes at least one corresponding antenna. Any type ofantenna(s) may be used including, for example, a dipole, a patch, ahelical antenna, an omni-directional antenna, and/or others.

Before a cluster 28 is able to communicate with a network access station16, the cluster must be formed. As described previously, the deviceswithin a cooperative cluster will communicate with one another usingintra-cluster wireless links. These intra-cluster links should be highquality links (e.g., high signal to noise ratios (SNRs), etc.) that arecapable of relatively high data rates. When high quality links existbetween the cooperating users, the users are able to exchange packetswith little cost in terms of power and bandwidth. Therefore, in at leastone embodiment, only wireless user devices that are capable ofsupporting high quality links with one another will be allowed to form acluster. For example, a user device may only be allowed to join aparticular cluster if a channel quality parameter associated with thedevice satisfies a predetermined condition (e.g., a channel coefficientfor a channel between the device and the other devices in the cluster isgreater than a threshold value). In one possible approach, a user devicemay be designated as a master for a cluster to control the formation ofthe group. This may be, for example, a first device that indicates adesire to form a cluster. The master device may then allow other devicesto join the cluster if they qualify. Measurements may be made of achannel quality of each candidate device with respect to each otherdevice within the cluster. In some embodiments, there may be a maximumnumber of devices that will be permitted to join a cluster. Othertechniques for establishing the cluster may alternatively be used.

The devices within a cluster will often be located much closer to oneanother than to the network access station. While the intra-clusterwireless links are high quality links, the channel between the clusterand the network access station 16 may suffer from effects such as pathloss, shadowing, and multi-path fading. It is assumed that quasi-staticchannel conditions exist for all devices within the network arrangement.That is, the channel coherence time for all of the links is much largerthan the frame duration and the channel coherence bandwidth iscomparable in magnitude to the transmit signal bandwidth. It is alsoassumed that the channel is unknown at the transmitters but known at thenetwork access station 16. In one embodiment, the network access stationor receiver may then be able to transmit, over a low bandwidth feedbacklink, transmission instructions or alternatively channel informationwhich allows the users to adapt their uplink transmission strategy andoptimize the link quality.

Two practical techniques for optimizing link quality (e.g. throughputand reliability) in MIMO based systems are antenna selection and linkadaptation. Antenna selection refers to the ability to transmit andreceive information over the most efficient antennas. While linkadaptation refers to the ability of the wireless device to switchbetween modulation schemes depending on the state of the channel. Invarious embodiments, the modulation schemes may be cooperativediversity, cooperative multiplexing, a hybrid cooperative mode, or anon-cooperative multi-access mode.

Referring to FIG. 3 a block diagram illustrating an example cooperativemultiple access wireless network arrangement wherein the wirelessdevices and network access stations are capable of antenna selection isshown. The arrangement includes two wireless user devices 312, 314 eachincluding: a receive block 301, 306, a signal generation block 302, 307,an RF chain 303, 308, a switch 304, 309, and a transmitting antennaarray including two antennas 305, 310. The transmitting antenna array ofthe wireless user device may include one or more antennas, and may becoupled to one or more RF chains. The arrangement also includes anetwork access station 340 including: a receive block 330, two RF chains324, 326, a switch 322, and a receiving antenna array including fourantennas 320. The receiving antenna array may include two or moreantennas, and may be coupled to one or more RF chains.

In one embodiment, each wireless user device and network access stationcomprises a reduced number of RF chains in relation to the number ofantennas in their respective transmitting and receiving antenna arrays.That is, the number of RF chains is less than or equal to the number ofantennas in the antenna array. For example, as shown in FIG. 3, eachuser device 312, 314 has a transmitting antenna array of two antennas305, 310, and employs only one RF chain 303, 308, respectively.Similarly, the network access station has a receiving antenna array 320comprising four antennas, and employs only two RF chains 324, 326. Giventhat a single RF chain may be utilized by only a single antenna at anygiven time, an antenna selection technique may be used to optimize thetransmitting and receiving antenna arrays. Namely, the network accessstation 340, with knowledge of the number of antennas and RF chains ofeach wireless device, may determine the optimal transmitting antennaarray subset for each wireless user device using antenna selectionalgorithms.

Antenna selection algorithms for MIMO networks are known in the art.These algorithms, however, are not applicable in cooperative multipleaccess systems. The known algorithms are applied in situations where asingle device has multiple antennas. Stated another way, known methodsof selecting antenna array subsets focus on selecting the subset fromone antenna array. In contrast, cooperative multi-access systems requireeach wireless user device to perform antenna selection independentlyfrom other wireless user devices. To illustrate this principle considerthe following with reference to FIG. 3; wireless user devices 312, 314are cooperating to communicate with network access station 340 as atransmit cluster 28. Each wireless user device 312, 314, has twoantennas and only one RF chain 303, 308, respectively. In calculatingthe optimal transmitting antenna array subset for the transmit cluster28, the network access station must choose one antenna from each device312, 314, even if for instance, both of the antennas on wireless userdevice 314 perform better than each antenna on wireless user device 312.Thus, the number of antenna subsets for antenna selection in acooperative multi-access system is less than that for a point-to-pointMIMO system, in which the transmit antenna array possesses the sametotal number of transmitting antennas as the cooperative multi-accesssystem.

Before a transmitting or receiving antenna array subset may bedetermined, however, the network access station 340, in one embodiment,first estimates the channel from the transmit cluster 28 to the networkaccess station 340. With knowledge of the wireless user devices 312, 314and the instantaneous channel characteristics, network access stationmay use a minimum Euclidean distance metric to determine the optimaltransmitting antenna array subset for each device, namely wireless userdevices 312, 314, and the network access station 340. The network accessstation may then transmit this information to each of the wireless userdevices 312, 314 within the transmit cluster 28. In another embodiment,the network access station may transmit only the channel characteristicsand allow the wireless user devices 312, 314 to determine an antennaarray subset independently. In still other embodiments, the transmissionis over a low bandwidth feedback link, and therefore, does not generatea bandwidth penalty within the primary communication network.

Once the transmitting and receiving antenna array subsets have beendetermined and transmitted to the transmit cluster 28, the individualwireless user devices 312, 314 may receive the transmission at receiveblock 301 and 306, respectively. Receive blocks 301, 305 may also beused to receive the bit streams from other wireless user devices withina common transmit cluster 28. In at least one embodiment, the receiveblock 301, 306 is operative in a different frequency band from thetransmitting antenna array. The received bit streams are then sent to asignal generation blocks 302, 307 to generate a modulated signal forpropagation into the MIMO channel. In various embodiments the modulatedsignal is modulated according to a modulation scheme which may be one ofcooperative diversity, cooperative multiplexing, a hybrid cooperativemode or a non-cooperative multi-access mode. Once the signal isgenerated, which will be discussed in more detail below, the signal ispassed to the RF chain and ultimately transmitted into the MIMO channelvia the determined transmitting antenna array subset. Switches 304 and309 act to couple the determined transmitting antenna array subset tothe available RF chains.

The network access station, having previously determined a receivingantenna array subset, may, in one embodiment, use switch 322 to couplethe receiving antenna array subset to the available RF chains forreceiving the transmitted communications from the transmit cluster 28.Network access station 340 may then use receive block 330 to demodulateand decode the data from the transmit cluster 28 and separate out thedata associated with each of the cooperating wireless user devices 312,314.

Referring to FIG. 4, a block diagram illustrating an example cooperativemultiple access wireless apparatus capable of performing linkadaptation, in accordance with various embodiments of the presentinvention, is shown. The apparatus 400 includes: a receive block 402, abit stream merger 404, a time frequency-coder/interleaver 406, first andsecond encoding paths 422, 420, and a transmitter 418. The transmitter,as shown, includes two antennas, but any number of antennas may be used.In one embodiment, the first and second encoding paths each work tomodulate a signal according to a different modulation scheme. The firstencoding path may include: a symbol modulator 408, a space-time codingblock 410, and a splitter 412. The second encoding path may include: asymbol modulator 414, and a splitter and de-multiplexer 416.

In at least one embodiment of the present invention, before data istransmitted to a network access station by the transmit cluster, thedevices of the cluster exchange data messages, through a receiver 402,that they wish to transmit to the network access station. The receiver402 may be operative in a different frequency band than that of thetransmitter. Additionally, the wireless apparatus may also receivetransmission instructions including a modulation scheme to be used, atransmitting antenna array subset to be used, and/or channelcharacteristics of the MIMO channel, through receiver 402. After thisdata exchange, each of the devices of the cluster have the messages ofthe other devices in the cluster and the transmission instructions fromthe network access station. The bit stream merger 404, within aparticular device, merges the bit streams of the other device(s) withinthe transmit cluster with the bit stream of the device itself to form amerged bit stream. Each of the other devices within the cooperativecluster also merge the bit streams together in the same fashion. Apriority scheme may be established so that each device knows the orderwith which to merge the bit streams. The merged bit stream is nextprocessed by the time-frequency coder and interleaver 406, which appliestime-frequency coding and interleaving to the stream to generate a codedbit stream. Although illustrated as a single unit, it should beappreciated that, in at least one embodiment, the time-frequency codingand interleaving may be performed separately. Each device within thecooperative cluster will apply the identical time-frequency code at thisstage.

The coded bit stream is then passed to one of two encoding paths 422 or420 to modulate the symbol according to a modulation scheme. In anembodiment as shown in FIG. 4, the first encoding path 422 is one ofcooperative diversity, and the second encoding path 420 is one ofcooperative multiplexing. If, for instance, cooperative diversity isdetermined to be the more efficient modulation scheme, the coded bitstream is provided to the first encoding path 422, and is firstmodulated into symbols by symbol modulator 408. The symbols are thenspace time encoded using the space-time encoder 410 to extract diversityand coding gains. A splitter 412 then takes the space-time encodedsymbols and splits them in a predetermined way such that each userwithin the transmit cluster transmits its portion of the coded symbols.In another embodiment, space-time block coding may be used, in whichcase each user may perform its space-time block coding operation on theinput symbols independently, and thus the splitting operation is notnecessary.

If, however, the cooperative multiplexing is determined to be the moreefficient modulation scheme, the coded bit stream is modulated intosymbols by symbol modulator 414. The symbols are then split by splitter416 in a predetermined way such that each user transmits its portion ofthe coded sequence. Each user then demultiplexes, by demultiplexer 416,its share of the coded and modulated symbols in to a number ofsubstreams, and each substream is transmitted on a different transmitantenna.

In another embodiment, the determination of which encoding scheme toutilize is made by a network access station having knowledge of theinstantaneous channel state from the network access system to thetransmit cluster in which the device 400 is a member. The network accessstation, in determining which scheme is optimal, fixes the rate oftransmission for both diversity coding and spatial multiplexing modes,and chooses the mode that yields the lowest error probability. In atleast one embodiment, a minimum Euclidean distance metric may be used.The spatial mode which maximizes the minimum Euclidean distance alsominimizes the error probability for a fixed target data rate.

In at least one embodiment of the present invention, the bit streammerging and the time frequency coding and interleaving discussed aboveare performed within a single device in the cluster. The resulting codedbit stream is then transmitted (e.g., broadcast, etc.) to all of thedevices within the cluster. The individual devices in the cluster maythen perform their corresponding splitting and transmit operations asdiscussed previously. In one implementation, additional coding is usedto protect the coded stream over the intra-cluster link(s) so that eachdevice receives the correct version of the coded bits.

FIG. 5 is a flowchart illustrating an example method 500 for performinglink adaptation and antenna selection in a cooperative multiple accesssystem, in accordance with an embodiment of the present invention.First, a network access station estimates the channel characteristicsfrom the network access station to the transmit cluster (block 502). Anynumber of devices (i.e. 2 or more) may be a part of the cluster. Thenetwork access station then determines a transmitting antenna arraysubset for each device and a receiving antenna array subset for thenetwork access station based on the channel characteristics (block 504).The transmitting antenna array and antenna array subset may contain anynumber of antennas (i.e. 1 or more antennas per device). The number ofantennas in the transmitting antenna array subset will be determined bythe number of available RF chains in each device. The receiving antennaarray and antenna array subset may contain any number of antennas (i.e.1 or more). The number of antennas in the receiving antenna array subsetwill be determined by the number of available RF chains at the receivingdevice. In at least one embodiment the transmitting and receivingantenna arrays (i.e. optimal subset of transmitting and receivingantennas) will be determined by the use of a minimum euclidean distancemetric. The network access station then determines a modulation schemebased on the channel characteristics (block 506). The modulation schememay be one of space-time cooperative diversity, space-time cooperativemultiplexing, a hybrid space-time cooperative mode, or a space-timenon-cooperative multi-access mode. In one embodiment, the network accessstation may determine the modulation scheme based upon the use of aminimum euclidean distance metric. In another embodiment, the antennaselection operation in block 504 and link adaptation operation in block506 can be performed jointly at the same time based on the channelcharacteristics by the use of a minimum euclidean distance metric.Thereafter, the network access station transmits the determinedtransmitting antenna array subset and the determined modulation schemeto the transmit cluster (block 510). In one embodiment the transmittingmay take place over a low bandwidth feedback link. In other embodimentsthe transmission may be received by a receive block which is operativein a different frequency band than the transmitting antenna array of theinstant device.

FIG. 6 is a flowchart illustrating an example method 600 of performinglink adaptation within a wireless device functioning in a cooperativemultiple access wireless network, in accordance with various embodimentsof the present invention. First, a wireless device receives bit streamsfrom other devices within a transmit cluster, merges the bits streams,and time-frequency codes and interleaves the bit streams to form a codedbit stream (block 602). In various embodiments the cluster may containany number of devices, and consequently, any number of bit streams maybe merged. At decision block 604, a decision is made regarding whichmodulation scheme is to be used to modulate the coded bit stream,spatial multiplexing or spatial diversity. In one embodiment, thisdecision is made by a network access station based on characteristics ofthe channel from the network access station to the transmit cluster. Inanother embodiment, the wireless device may decide which modulationscheme to use. In still other embodiments, various other metrics knownin art may be used to decide an optimal modulation scheme. Assumingspatial diversity is chosen, the jointly coded bit streams are modulatedinto symbols (block 606). Next, the modulated symbols are space-timeencoded to extract diversity and coding gains (block 608). Finally, asplitting operating on the space-time encoded symbols is made in apredetermined way such that each user transmits only its portion of themodulated signal (block 610). If at block 604 it is decided that spatialmultiplexing is the optimal modulation scheme, the jointly coded bitstreams are first modulated into symbols (block 612). At block 614, asplitting operation is performed on the modulated symbols which are thendemultiplexed into substreams so that each users transmits only itsportion of the coded bit stream.

The techniques and structures for practicing embodiments of the presentinvention may be implemented in any of a variety of different forms. Forexample, various features may be embodied within laptop, palmtop,desktop, and tablet computers having wireless capability; personaldigital assistants (PDAs) having wireless capability; cellulartelephones and other handheld wireless communicators; pagers; satellitecommunicators; cameras having wireless capability; audio/video deviceshaving wireless capability; network interface cards (NICs) and othernetwork interface structures; base stations; wireless access points;integrated circuits; as instructions and/or data structures stored onmachine readable media; and/or in other formats. Examples of differenttypes of machine readable media that may be used include floppydiskettes, hard disks, optical disks, compact disc read only memories(CD-ROMs), digital video disks (DVDs), Blu-ray disks, magneto-opticaldisks, read only memories (ROMs), random access memories (RAMs),erasable programmable ROMs (EPROMs), electrically erasable programmableROMs (EEPROMs), magnetic or optical cards, flash memory, and/or othertypes of media suitable for storing electronic instructions or data. Inat least one form, the invention is embodied as a set of instructionsthat are modulated onto a carrier wave for transmission over atransmission medium. As used herein, the term “logic” may include, byway of example, software or hardware and/or combinations of software andhardware.

It should be appreciated that the individual blocks illustrated in theblock diagrams herein may be functional in nature and do not necessarilycorrespond to discrete hardware elements. For example, in at least oneembodiment, two or more of the blocks in a diagram are implemented insoftware within a single digital processing device. The digitalprocessing device may include, for example, a general purposemicroprocessor, a digital signal processor (DSP), a reduced instructionset computer (RISC), a complex instruction set computer (CISC), a fieldprogrammable gate array (FPGA), an application specific integratedcircuit (ASIC), and/or others, including combinations of the above.Hardware, software, firmware, and hybrid implementations may be used.

In the foregoing detailed description, various features of the inventionare grouped together in one or more individual embodiments for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted as reflecting an intention that the claimedembodiments of the invention require more features than are expresslyrecited in each claim. Rather, as the following claims reflect,inventive aspects may lie in less than all features of each disclosedembodiment.

Although certain embodiments have been illustrated and described hereinfor purposes of description of the preferred embodiment, it will beappreciated by those of ordinary skill in the art that a wide variety ofalternate and/or equivalent embodiments or implementations calculated toachieve the same purposes may be substituted for the embodiments shownand described without departing from the scope of the present invention.Those with skill in the art will readily appreciate that embodiments inaccordance with the present invention may be implemented in a very widevariety of ways. This application is intended to cover any adaptationsor variations of the embodiments discussed herein. Therefore, it ismanifestly intended that embodiments in accordance with the presentinvention be limited only by the claims and the equivalents thereof.

1. A method comprising: estimating, by a network access station, channelcharacteristics of a channel from the network access station to atransmit cluster, the network access station having an antenna array ofat least one antenna, and the transmit cluster comprising at least twowireless devices each comprising a transmitting antenna array of atleast one antenna; determining, by the network access station, atransmitting antenna array subset of the transmitting antenna array foreach wireless device within the transmit cluster based on at least thechannel characteristics; determining, by the network access station, amodulation scheme for communication via the channel based on at leastthe channel characteristics; and transmitting, by the network accessstation, the determined transmitting antenna array subset for eachwireless device and the determined modulation scheme to the wirelessdevices to facilitate communication between the transmit cluster and thenetwork access station.
 2. The method of claim 1 further comprising,determining, by the network access station, a receiving antenna arraysubset of the receiving antenna array for the network access stationbased on at least the channel characteristics.
 3. The method of claim 2,wherein the determining, by the network access station, the transmittingantenna array subset, the receiving antenna array subset, and themodulation scheme comprises the network access station employing aminimum euclidean distance metric to determine the transmitting antennaarray subset, the receiving antenna array subset, and the modulationscheme.
 4. The method of claim 1, wherein the transmitting is via a lowbandwidth feedback link.
 5. The method of claim 1, wherein themodulation scheme for communication via the channel comprises one ofspace-time cooperative diversity, space-time cooperative multiplexing, ahybrid space-time cooperative mode, or a space-time non-cooperativemulti-access mode.
 6. An apparatus comprising: a receive block toreceive transmission instructions from a network access station and bitstreams from at least a wireless device in a common transmit cluster; asignal generation block coupled to the receive block to generate aMultiple Input Multiple Output (MIMO) signal based on at least thetransmission instructions; at least one RF chain coupled to the signalgeneration block to facilitate transmission of the MIMO signal into aMIMO channel; an antenna array comprising at least one antenna coupledto the signal generation block to transmit the MIMO signal into the MIMOchannel; and a switch coupled to the at least one RF chain and theantenna array to facilitate a connection between the at least one RFchain and the at least one antenna according to the transmissioninstructions.
 7. The apparatus of claim 6, wherein the transmissioninstructions comprise a modulation scheme to be used in generating theMIMO signal, and an antenna array subset to be used in transmitting theMIMO signal.
 8. The apparatus of claim 7, wherein the modulation schemeis one of space-time cooperative diversity, space-time cooperativemultiplexing, a space-time hybrid of cooperative diversity andcooperative multiplexing, or a non-cooperative multi-access scheme. 9.The apparatus of claim 6, wherein the number of RF chains is less thanor equal to the number of antennas in the antenna array.
 10. Theapparatus of claim 6, wherein the transmission instructions are receivedover a low bandwidth feedback link.
 11. The apparatus of claim 6,wherein the receive block is operative in a different frequency bandfrom the antenna array.
 12. The apparatus of claim 6, wherein thetransmission instructions were generated using a minimum euclideandistance metric.
 13. A system comprising: an antenna array comprising atleast one omni-directional antenna to transmit a MIMO signal into a MIMOchannel; a bit stream merger to merge a bit stream of a wirelessapparatus with at least one bit stream associated with a wireless devicein a common transmit cluster to form a merged bit stream, wherein thebit stream of the wireless apparatus and the at least one bit streamassociated with the wireless device are to be transmitted to a networkaccess station by the transmit cluster, via the MIMO channel; atime-frequency encoder and interleaver to time-frequency encode andinterleave the merged bit stream to generate a coded bit stream; and atleast a first and second encoding path, each coupled to the timefrequency coder and interleaver, and the antenna array, wherein thefirst encoding path modulates the coded bit stream according to a firstmodulation scheme and the second encoding path modulates the coded bitstream according to a second modulation scheme.
 14. The system of claim13, wherein the first modulation scheme is a space-time cooperativediversity, and the second modulation scheme is space-time cooperativemultiplexing.
 15. The system of claim 13, wherein the first encodingpath comprises: a symbol modulator coupled to the time-frequency coderand interleaver to modulate the coded bit stream into symbols; aspace-time encoder coupled to the symbol modulator to generate a numberof space-time encoded symbols equal to the number of antennae in theantenna array; and a splitter coupled to the space-time encoder to splitthe space-time coded symbols into multiple portions, the multipleportions including at least a first portion corresponding to thewireless apparatus's space-time coded symbols, and a second portioncorresponding to the wireless device's space-time coded symbols.
 16. Thesystem of claim 13, wherein the second encoding path comprises: a symbolmodulator coupled to the time-frequency coder and interleaver tomodulate the coded bit stream into symbols; a splitter coupled to thesymbol modulator to split the symbols into multiple portions, themultiple portions including a first portion, corresponding to thewireless apparatus's coded symbols, and at least one other portioncorresponding to the wireless device's coded symbols; and ademultiplexer coupled to the symbol modulator and splitter todemultiplex the first portion of the modulated symbols into a number ofsubstreams.
 17. The system of claim 13, further comprising a receivercoupled to the bit stream merger to receive the at least one bit streamfrom the wireless device.
 18. The system of claim 17, wherein thereceiver is operative in a different frequency band than the antennaarray.
 19. The system of claim 13, further comprising at least one RFchain coupled to the first and second encoding paths and the antennaarray to facilitate transmission of the modulated coded bit streams intothe MIMO channel.
 20. The system of claim 19, wherein the number of RFchains is less than or equal to the number of omni-directional antennasof the antenna array.